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программа для андроид чтобы открывать книги скачать, Polymer vs. Plastic: What Are the Differences? - Xometry, Plastic - Wikipedia, Plastic - Polymers, Synthetic, Recycling | Britannica, Plastic vs. Polymer - What's the Difference? | This vs. That, 7.9: Polymers and Plastics - Chemistry LibreTexts, The 7 Different Types of Plastics, Polymers vs. Plastics: What is the difference? - Stahl.
Properties The physical state and morphology of a polymer have a strong influence on its mechanical properties. A simple measure of the differences produced in mechanical behaviour is the that occurs when a plastic is loaded (stressed) in tension. A glassy polymer such as polystyrene is quite stiff, showing a high ratio of initial stress to initial elongation. On the other hand, polyethylene and , two highly crystalline plastics, are usable as films and molded objects because at room temperature their amorphous regions are well above their glass transition temperatures. The leathery toughness of these polymers above Tg results from the crystalline regions that exist in an amorphous, rubbery matrix. Elongations of 100 to 1,000 percent are possible with these plastics. In , another semicrystalline plastic, the crystalline portions exist in a glassy matrix because the Tg of PET is above room temperature. This gives the material a stiffness and high dimensional stability under stress that are of great importance in beverage bottles and recording tape. Almost all plastics exhibit some elongation on being stressed that is not recovered when the stress is removed. This behaviour, known as “,” may be very small for a plastic that is well below its Tg, but it can be significant for a partly crystalline plastic that is above Tg. The most commonly specified mechanical properties of polymers include stiffness and breaking stress, quantified in the table of properties and applications as flexural modulus and . Another important property is , which is the energy absorbed by a polymer before failure—often as the result of a sudden impact. Repeated applications of stress well below the tensile strength of a plastic may result in fatigue failure. Most plastics are poor conductors of heat; can be reduced even further by incorporating a gas (usually air) into the material. For instance, foamed polystyrene used in cups for hot beverages has a about one-quarter that of the unfoamed polymer. Plastics also are electrical insulators unless especially designed for conductivity. Besides conductivity, important electrical properties include dielectric strength (resistance to breakdown at high voltages) and (a measure of the energy dissipated as heat when an is applied). Additives In many plastic products, the polymer is only one constituent. In order to arrive at a set of properties appropriate to the product, the polymer is almost always combined with other ingredients, or additives, which are mixed in during processing and fabrication. Among these additives are , colorants, reinforcements, and stabilizers. These are described in turn below. Plasticizers Plasticizers are used to change the Tg of a polymer. (PVC), for instance, is often mixed with nonvolatile liquids for this reason. Vinyl siding used on homes requires an unplasticized, rigid PVC with a Tg of 85 to 90 (185 to 195 °F). A PVC garden hose, on the other hand, should remain flexible even at 0 °C (32 °F). A mixture of 30 parts di(2-ethylhexyl) phthalate (also called dioctyl phthalate, or DOP) with 70 parts PVC will have a Tg of about −10 °C (15 °F), making it suitable for use as a garden hose. Although other polymers can be plasticized, PVC is unique in accepting and retaining plasticizers of widely varying chemical composition and molecular size. The plasticizer may also change the flammability, odour, , and cost of the finished product. For most consumer applications, plastics are coloured. The ease with which colour is incorporated throughout a molded article is an advantage of plastics over metals and ceramics, which depend on coatings for colour. Popular pigments for colouring plastics include and zinc oxide (white), (black), and various other inorganic oxides such as iron and chromium. Organic compounds can be used to add colour either as pigments (insoluble) or as dyes (soluble). Reinforcements, as the name suggests, are used to enhance the mechanical properties of a plastic. Finely divided silica, , talc, mica, and , as well as short fibres of a variety of materials, can be incorporated as particulate . (The use of long or even continuous fibres as reinforcement, especially with thermosets, is described below in .) Incorporating large amounts of particulate filler during the making of plastics such as polypropylene and polyethylene can increase their stiffness. The effect is less dramatic when temperature is below the polymer’s Tg. In order for a plastic to have a long and useful life in any application, the properties of that plastic should change as little as possible with time. Stabilizers are added, usually in small quantities, to counter the effects of aging. Because all carbon-based polymers are subject to oxidation, the most common stabilizers are . Hindered and tertiary are used in plastics in concentrations as low as a few parts per million. For example, butylated hydroxytoluene (BHT) is used in packaging films for foods and pharmaceuticals. PVC requires the addition of heat stabilizers in order to reduce dehydrohalogenation (loss of [HCl]) at processing temperatures. Zinc and calcium soaps, organotin mercaptides, and organic phosphites are among the many additives found to be effective. Other stabilizers are designed specifically to reduce degradation by sunlight, ozone, and biological agents. , Polymers are materials composed of repeating chains of smaller molecular units called monomers. Polymers can be naturally occurring (such as cellulose, latex, and rubber) or synthetic (like nylon, polyethylene, and polypropylene). The terms “polymer” and “plastic” are often used interchangeably, but there are noticeable differences between the two. Plastics are mostly synthetic , Most plastics contain organic polymers. [12] The vast majority of these polymers are formed from chains of carbon atoms, with or without the attachment of oxygen, nitrogen or sulfur atoms. These chains comprise many repeating units formed from monomers. Each polymer chain consists of several thousand repeating units. The backbone is the part of the chain that is on the main path, linking .
Plastic - Polymers, Synthetic, Recycling: Polymers are chemical compounds whose molecules are very large, often resembling long chains made up of a seemingly endless series of interconnected links. The size of these molecules, as is explained in chemistry of industrial polymers, is extraordinary, ranging in the thousands and even millions of atomic mass units (as opposed to the tens of atomic , Plastic vs. Polymer What's the Difference? Plastic and polymer are often used interchangeably, but they have distinct differences. Plastic is a type of polymer, which refers to a large molecule made up of repeating subunits called monomers. While plastic is a specific type of polymer that can be molded into various shapes, polymers encompass a broader range of materials, including natural , Plastics and natural materials such as rubber or cellulose are composed of very large molecules called polymers. Polymers are constructed from relatively small molecular fragments known as monomers that are joined together. Wool, cotton, silk, wood and leather are examples of natural polymers that have been known and used since ancient times. This group includes biopolymers such as proteins , This system divides plastics into seven distinct categories according to their chemical structure and polymer composition. By having an organised way to identify different types of plastic materials, it has become easier for manufacturers, recyclers, and waste specialists alike to categorise them properly., What is the future of polymers and plastics? The latest developments in polymer and plastic technology focus on reducing the planetary impact of synthetic polymers. Bio-based polymers, for instance, are produced from renewable feedstocks and can also be biodegradable. The market for these products is expected to reach USD 29.7 billion by 2026., Plastics VS Polymers Polymers may be found in nature or created synthetically, composed of sequences of monomers or singular molecules. Contrarily, plastics represent a distinct category of polymers, comprised of polymer chains that might be semi-organic or wholly synthetic..